Lipidic particles may be complexed with virtually any biological material. This capability allows these complexes to be useful as delivery systems for proteins, therapeutic agents, chemotherapeutic agents and nucleic acids. Although lipidic complexes have been used for a myriad of drug therapies, one area where these delivery systems have shown promising results is in gene therapy. For gene therapy to be successful efficient and safe transfer of genes or biologically active reagent to a target cell is required. Hence the need for improved delivery systems, in both conventional and gene-based therapies is always at the forefront.
Lipidic particles have been shown to be efficient vehicles for many in vitro and in vivo applications. Lipidic particles complexed with DNA have been used in vitro (Felgner et al. (1987); Gao et al. (1991)) and in vivo (Nabel et al. (1990); Wang et al. (1987); Zhu et al. (1993); Soriano et al. (1983)) for the expression of a given gene through the use of plasmid vectors.
Formation of complexes of DNA with cationic lipidic particles has recently been the focus of research of many laboratories. Improved formulations of cationic lipids have greatly increased the efficiency of DNA delivery to cells in tissue culture (Felgner et. al. (1987)). In contrast, intravenous DNA delivery in animals using cationic liposomes has been less efficient (Zhu et al. (1993); Philip et al. (1993); Solodin et al. (1995); Liu et al. (1995); Thierry et al. (1995); Tsukamoto et al. (1995); Aksentijevich et al. (1996)) limiting the therapeutic application of nonviral vectors to gene therapy. Improved liposome formulations for in vivo delivery is a valuable alternative to gene therapy using viral vectors and avoids several problems associated with viral delivery. Although efforts to synthesize new cationic lipids led to the discovery of more efficient transfection agents, their efficiency measured in tissue culture does not correlate with ability to deliver DNA after systemic administration in animals (Solodin et al. (1995)). Functional properties defined using in vitro experiments do not assess stability of the complexes in plasma or their pharmacokinetics and biodistribution, all of which are essential for in vivo activity (Felgner et al. (1994)). Colloidal properties of the complexes in addition to the physicochemical properties of their component lipids may determine these parameters.
The liposome provides an alternative to viral delivery systems in gene therapy which may involve the transfer of normal, functional genetic material into cells to correct an abnormality due to a defective or deficient gene product. Typically, the genetic material to be transferred should at least contain the gene to be transferred together with a promoter to control the expression of the new gene.
Methods for viral DNA delivery systems suffer from many inherent problems including immune responses, inability to deliver viral DNA vectors repeatedly, difficulty in generating high viral titers, and the possibility of infectious virus. Non-viral delivery methods provide an alternative system that is devoid of these problems. However, until now, low efficiency of DNA (“ρ”) of about 2.
The present invention further relates to a method of preparing these novel liposomes comprising the steps of heating, sonicating, and extrusion of the liposome structures. The method of preparation of the present invention produces complexes of appropriate and uniform size, which are structurally stable and produce maximal extrusion. Liposomes prepared by this method are also encompassed by the present invention.
The present invention further relates to a novel liposome structure capable of carrying nucleic acids. The present invention also relates to an improved liposome formulation comprising DOTAP (1,2-bis(oleoyloxy)-3-(trimethylammonio)-propane) and cholesterol (“Chol”) and a nucleic acid which produces exceptionally high gene expression and protein production in vivo. These formulations are extremely stable, homogeneous in size, and can complex nucleic acids over a wide range of nucleic acid:liposome ratios. The present invention demonstrates up to 150-fold greater gene expression following in vivo systemic delivery in animals as compared to formulations previously described in the literature.
The present invention also relates to liposomes carrying non-immunogenic targeting ligands and stealth lipids. These ligands facilitate the targeted delivery of the liposomes to a particular tissue or site in the body.
The present invention relates to kits containing the present liposome structure capable of carrying a reagent within it. One such kit may comprise the liposome structures ready for the user to add the biological reagent of interest. A kit may further comprise a liposome preparation and one or more specific biologically-active reagents for addition to the liposome structure. Another kit of the present invention comprises a set of liposome structures, each containing a specific, biologically-active reagent, which when administered together or sequentially, are particularly suited for the treatment of a particular disease or condition.
The present invention provides a therapeutic method of treating diseases, ailments and conditions based upon a liposome-facilitated delivery of biologically active agents. For example, the present invention provides a pharmaceutical liposomal formulation for the delivery of nucleic acids using systemic administration to provide long-term expression of a given nucleic acid. In addition, the present invention encompasses in vitro cell transfection followed by tissue transplantation such that the transfected cells may be incorporated in transplanted tissue. This method is referred to as in vitro/ex vivo transfer. Other biologically-active agents may be encapsulated in the liposomes of the present invention for in vitro/ex vivo methods so long as a +/−charge of positive 2 is maintained.
The present invention further provides an effective vaccine vehicle capable of effective delivery, boosting antigen-immune response and lowering unwanted extraneous immune response, presently experienced with adjuvants.